>> susie: investors loved the deal, shares of both companies were up sharply today. erika miller has more on what's behind the merger, and what it will mean for consumers. >> reporter: for southwest, a big reason for the merger is the southeast. the discount airline carries more passengers in the united states than any other, including the big boys. but analyst jim corridore says southwest has been missing one key, lucrative market. >> airtran presents a very compelling opportunity, because they have a big foothold in atlanta, which is a market southwest doesn't serve. that's a great business market, and southwest is focusing on attracting more business travelers, so that's a nice fit for them. >> reporter: in addition to atlanta, southwest will gain coveted slots in other top business markets, like new york and d.c. morningstar's basili alukos says the acquisition also makes sense for southwest because it wipes out one its biggest rivals. >> airtran has a younger fleet. they have a younger workforce. and those go against southwest because, as a result, airtran has a lower cost structure, so that allows them to compete. it allows them to reduce costs.